A naturally occurring inhibitor, Cell Regulatory Sialoglycopeptide (CeReS-18), has been isolated and purified from the surface of cells. In short term assays it causes nontoxic, completely reversible, quiescence. Removal causes striking synchronization allowing the isolation of a homogeneous population of cells in any position in the cell cycle. The goal of this proposal is to determine if it is feasible to use the properties of CeReS-18 to develop model systems useful to researchers studying aging. Attempts to isolate cells in identical growth conditions at each stage and at each hour of the cell cycle will be made. Quiescence without crowding or nutrient starvation is anticipated Long term CeReS-18 exposure will be examined for the first time. Cellular growth properties will be studied. Molecular studies have demonstrated that cells treated with CeReS have the second major aim of this study is to determine if it is feasible to use CeReS-18 to study molecular events that are associated with progression through specific stages of the cell cycle, and the quiescence/senescence transition.